Direct inking platen

ABSTRACT

An inking platen suitable for use with impact printers and comprising a unitary microporous nylon body having a thin microporous flexible tough outer skin portion, and a ribbon affixed to the skin; the ribbon being woven of nylon fibers, the body being compression molded from a predetermined particulate nylon blend of a minority of high mesh nylon and the remainder of low mesh nylon.

United States Patent 1191 Neumann et al.

[ Aug. 5, 1975 1 DIRECT lNKlNG PLATEN [75] Inventors: Edward W. Neumann; William C.

Thomas, both of Raleigh, N .C.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: Jan. 30, 1974 [2]] Appl. No.: 438,113

Related US. Application Data [63] Continuation of Ser. No. 220,956. Jan. 26, 1972,

abandoned.

[52] US. Cl. 428/265; 101/197; 101/327; 118/264; 264/122; 428/305; 428/306;

[51] Int. Cl. B30B 15/06 [58] Field of Search 118/260, 264; 101/1282, 101/395. 327,197; 161/401, 159, 89, 160; 264/122 [56] References Cited UNITED STATES PATENTS 3,022,542 2/1962 Davis 101/395 3,312.193 4/1967 Satas 118/264 3,713,936 1/1973 Ramsay 3,718,116

2/1973 Thetto 118/60 Primary ExuminerGeorge F. Lesmes Assistant E.\'uminer--,lames J. Bell Attorney, Agent, or Firm-Edward H. Duffield 57 ABSTRACT An inking platen suitable for use with impact printers and comprising a unitary microporous nylon body having a thin microporous flexible tough outer skin portion, and a ribbon affixed to the skin; the ribbon being woven of nylon fibers, the body being compression molded from a predetermined particulate nylon blend of a minority of high mesh nylon and the remainder of low mesh nylon.

4 Claims, 1 Drawing Figure DIRECT INKING PLATEN This is a continuation, of application Ser. No. 220,956 filed 1-26-72, now abandonded.

BACKGROUND OF THE INVENTION This invention relates to a direct inking platen, and more particularly to improvements in the ink flow, wear resistance, and print definition characteristics thereof.

In the prior art, impact printers would either urge an inking surface toward the paper or vis a vis. In U.S. Pat. No. 2,414,895 issued to M. Reynolds ct al on Jan. 28, 1947, an operating bar impacts a porous print element through an ink filled flexible diaphragm-like reservoir. Compression of the reservoir and the mechanical engagement of the print element provided contact with the paper and also served to transfer ink from the reservoir to the print element.

Another form of impact printer termed a wire matrix printer is illustrated in U.S. Pat. No. 3,198,306 to R. A. Bachman on Aug. 3, 1965, and utilizes a plurality of individually operable dot printing elements such as spaced apart parallel wires. The wires are simultaneously projected in combination against an ink ribbon to effect printing of the whole character at once by the ribbon upon the paper. Characteristically, ribbon printing with wires suffers due to wearing of the wires impacting the ribbon and the deterioration of the ribbon due to the shredding of its fibers by the progressively worn and sharpened wires. While the exact mechanism of wearing of the wires is not fully understood, it is believed that it is due to a combination of factors such as chemical and hydraulic etching of the wire ends by the inking medium as well as mechanical impact deformation.

Of course, one approach is to eliminate the ribbon inking medium entirely. This may be accomplished by using self-inking paper. That is, the paper changer color due to localized pressure changes when impacted by the wires. This approach suffers the disadvantage of the high cost of specially treated paper, fragility, and tendency to discolor when mechanically handled.

Admittedly, the prior art is replete with many self inking sponge-like structures ranging from the rubber used by Reynolds et al to the porous polyamide articles described in U.S. Pat. No. 3,022,542, issued to W. J. Davis on Feb. 27, 1962. Reference should also be made to the porous plastic printing structures shown in U.S. Pat. No. 3,303,146 to P. Chabiniak issued Feb. 7, 1967. The prior art teaches in general terms that an inking platen having microporous structure can be formed from the compression molding of particulate nylon or polyvinylchloride. These sponge-like structures, however. would be proverbially torn to shreds under repeated wire firings in a wire matrix printer, for example. It is also the case that the impacting of sponge-like structures, even with the same force, results in dissimilar quantities of liquid being ejected therefrom. Lastly, such structures frequently have their pores randomly distributed. This means that the print character may lack good definition. i.e., the dot print elements lack regular and uniform spacing.

SUMMARY OF THE INVENTION It is accordingly an object ofthis invention to devise a direct inking platen capable ofwithstanding repeated deformation from impacting printing mechanisms such as a wire firing dot matrix printer. It is a related object that the platen should resist deformation of its surface, render more uniform the flow of ink, and exhibit improved print definition.

The foregoing objects are satisfied in an embodiment of a direct inking platen comprising a unitary nylon body having microporous interstices and a flexibletough microporous outer skin, the body being formed from a compression molded particulate nylon blend. A ribbon of woven nylon fibers is affixed to the body, preferably by heat fusion, and both covers and is in contact with the flexible-tough outer skin.

It was unexpectedly discovered that by compression molding a particulate nylon blend containing a calculated minority of high mesh nylon with the remainder of low mesh nylon under a certain range of pressure, temperature, and duration, that a microporous nylon body and microporous flexible-tough outer skin could be formed. The micropores were sufficient to ooze an oil based liquid medium throughout the body by capillary action. The porous flexible-tough outer skin would withstand repeated impacts. Now, if the compression molding conditions of the blend lay outside the critical ranges, then a body having the desired characteristics cannot be formed. Thus, if the duration of the mold is exceeded, a flexible tough impervious skin results.

It is noteworthy that the nylon ribbon with its regularly spaced interstices is in intimate contact with the randomly spaced micropores of the flexible-tough skin. The ribbon is of sufficient thickness to wick the oil based liquid (ink) from the micropores to the other side of the ribbon. When papersuddenly urged against the ribbon by an impacting means, (hammer, wires) then good definition is achieved by the uniform ribbon ink filled interstices. Liquid flow is controlled by the hydrostatic pressure between the ink filled ribbon and the micropores. Significantly, upon impact, the body skin deforms without tearing or shredding absorbing the impact energy. The body and skin possess sufficient resilience to return to their former shape when the impact or printing element is removed.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a cutaway side view of the inking platen according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The best mode for practicing the invention contemplates forming a nylon body from compression molding a particulate blend of nylon 6, 6. In this regard, nylon 6, 6 is understood to mean the polymer formed from the reaction product of hexamethylenediamine and hexane dioic acid. The resulting polymer possesses a melting point between 493F and 500F, and a nominal molecular weight of 17,500.

Bulk nylon is rendered into particles by milling or grinding. Particle size is determined by taking the ground particles and pouring them through a nest of sieves having progressively smaller apertures (increasing mesh size). The grinding and passing through the sieve occur at the same time. The sieve analysis consists "of taking a measured amount of material and placing it inthe topmost (coarsest) sieve and then shaking the material through the progressively finer openings. The residue at each sieve stage constitutes material coarser than the given mesh opening. The nominal mesh" of particulate materials is defined according to the ASTM Specification for Wire Cloth Sieves as utilized according to the ASTM test method for particle size by sieve analysis of plastic materials D 1921.

Now, it has been observed. also, that a structure obtained from the compression molding of a blend of different particle size nylon varies in the size of the interstitial spaces. Further, if large and small particles are mixed (blended) then the filled volume (packing fraction) can be increased. Relatedly. the degree of reenforcement for structural purposes is a function of filled volume. The justification for a particular blend is that it provides the optimum interstitial space. In the preferred embodiment.-the interstitial space was of a size sufficient to transport an oil based ink of viscosity between 100 to 125 centipoises at a temperature between 40 to l25F by capillary action. This corresponds to an approximate volumetric porosity of to [5%. Consequently, while all dye stuff based inks may be used, it is not expected that pigmented inks could be employed. Pigmented inks, in contrast with dystuff inks, contain ground up solids such as carbon black dispersed in a vehicle. Any concentration of the solids tends to-clog' the micropores, thereby inhibiting ink flow.

With the above background, it is desirable to describe the method according to the invention. In order to form the microporous platen, a particular blend of approximately 30% nominal eighty mesh nylon and 70% nominal twenty mesh nylon is compression molded for a period between ten to twenty minutes. The pressure upon the molded article varies between about l0,000'to- 15,000 psia at a temperature between about350F to 420F. The resulting structure is microporous with a flexible tough microporous thin skin in the order of 1/5000 inches thick therearound. The resilient' skin strongly contrasts with the interiorwhich might be best described as crumbly and having a porosity on the order of 5 to l5% by volume. If the blend is processed in excess of twenty minutes, at a temperature in excess of 420F, or at a pressure substantially exceeding 15,000 psia, then a non-porous skin is formed. This condition is believed due to formation of a melt of sufficient continuity to eliminate the desired porosity.

By using the optimum compression molding conditions, a porous tough thin skinned platen containing and supporting a weak structured interior is obtained. The skin exhibits a resilience and absorbs and dissipates the repeated point impact of an 11 mil diameter wire such as is found in a wire matrix printer. The structure has withstood up to 72,000,000 equivalent wire fires of the IBM 2,213 Printer. The print head characteristics of this wire matrix printer include a print rate of 66 characters/sec. a character matrix of five dots by of 183 i 3.5 lengthwise. fill count 114 :2: 3 crosswise;

a minimum thread count of 293, and caliper of 0.0033 1' .0003 inches was used with good effect.

Referring now to the FIGURE, there is shown a cross-section view of the preferred embodiment. in its contemplated use, the platen forms a directly inked arcuate surface against which selected portions of paper are urged 5 by an impact means such as wires (not shown) A. dotprinting mechanism, such as a wire cross-section, distorts the paper and deforms the ribbon. Toa lesser extent, the supporting flexible tough surface is likewise distorted. lnk which has been wicked through the ribbon is transferred from the ribbon to the paper. Upon removal of the wire. the platen possesses sufficient elastic response to return to its undistorted shape.

The nylon ribbon 1 may be conveniently heat fused to the skin 3 without altering the microporosity of either. The skin entirely surrounds and encloses the crumbly structured micro-porous interior 5. The nylon body is compression molded into its arcuate shape suitable for fabrication. An ink reservoir made from a suitable fiber filled medium 7 such as-felt is positioned on the opposite side of the body. A container 9 adapted to support the inking platen and reservoir may be fashioned from plastic or other material.

The ribbon, in addition to increasing platen life. improves definition due to the regularity of its interstices in contrast to the irregularity or random distribution of the micropores on the skin surface. The ribbon improves the inking efficiency because of its greater surface to volume ratio permits retention of a quantity of ink. For best results, a ribbon 3 mils thick should be used. It is recalled that as thickness is increased, definition is decreased. Also, as thickness is increased, wear life increases. At the same time as the nylon body inhibits forward movement of the impacting wire, it also serves as an ink reservoir and transfer medium to the ribbon. I:

The exact nature of the cohesive forces holding the hot pressed nylon together are not well understood. it is believed that the bonding yielding the unexpected results may be due to hydrogen bonding and that the bonding is interrather than intramolecular. The nylon particulate blend is hot pressed below its bulk melting point. Conceivably, in the hot pressing of the blend, certain sites on the surface constitute high energy nucleation sites and that adjacent particles would be accordingly joined. It is theorized that, in the embodiment, the number of fusion concentration sites would be in a minority compared to the hydrogen bonding sites. Probably, the hot pressing under the conditions previously set forth does not constitute sintering as that term is used in the art. That is, sintering is the process of making an open (porous) structure by fusing at selected sites under the influence of pressure and temperature. A mechanism analogous to that of the invention is considered to be that of the hydrogen bonding in hot pressed cellulosics.

Whilethe invention has been particularly shown and described as to preferred embodiments thereof; it will be understood by those of skill in the art that various changes in form and detail may'be made without departing from the spirit and scope of the invention.

What is claimed is:

l. A direct inking platen comprising: i

a unitary nylon body havingmicroporous interstices 1 and an integral flexible-tough microporous outer skin portion, said body and skin being formed from a compression particulate nylon blend. said blend containing a minority of high mesh nylon particles with the remainder of low mesh nylon particles;

said blend being compressed at a temperature from approximately 350 to 420F and at a pressure from approximately 10,000 psia to 15,000 psia for a duration of at least ten minutes and less than 20 minutes; and

a ribbon formed from a weave of nylon fibers and affixed to said body, the ribbon covering and being contiguous with at least a portion of said flexibletough outer skin.

2. A direct inking platen comprising:

unitary nylon body and skin compression molded from a particulate nylon blend of disparate mesh nylon particles, said body having microporous interstices capable of transferring an oil based liquid medium throughout said body by capillary action, said body further having an integral flexible-tough outer skin portion, the micropores of which are randomly distributed;

said body and skin being formed by compression molding of said blend of nylon particles at a temperature from approximately 350F to approximately 420F and at a pressure from approximately 10,000 psia to 15,000 psia for a duration of at least ten minutes and less than twenty minutes; and

a ribbon formed from a weave of nylon fibers affixed to said body, said ribbon having substantially uniformly spaced interstices, the ribbon covering and being contiguous with at least a portion of said flexible-tough outer skin.

3. A direct inking platen comprising: a unitary microporous nylon body having a porosity of from approximately 57z to approximately and an integral flexible-tough microporous outer skin portion having a thickness on the order of approximately 1/5000 inches, said microporous inter- 6 stices of said body being randomly distributed and capable of transferring an oil based liquid medium throughout said body by capillary action;

said body and skin being formed from a compression molded blend of nylon particles, said blend being of a minority of nominal mesh and the remainder of nominal 20 mesh particles, and being compressed at a temperature in the range from approximately 350F to approximately 420F and at a pressure in the range from approximately 10,000 psia to 15,000 psia for a duration of at least ten minutes and less than twenty minutes; and

' ribbon affixed to said body formed from a nylon fiber weave of nominal warp count of and nominal fill count of 1 15, and of a thickness from approximately 0.0030 inches to 0.0036 inches, said ribbon covering and being contiguous with at least a portion of said flexib1etough outer skin.

4. A direct inking platen comprising: a unitary microporous nylon body capable of trans ferring an oil based liquid medium therethrough by capillary action and further having an integral flexible-tough microporous outer skin portion, said body and skin being formed from a compression molded blend of nylon particles, said blend being composed of a minority of nominal eighty mesh particles and the remainder of nominal twenty mesh particles, and being compressed at a temperature in the range from approximately 350 to approximately 420F, at a pressure in the range from approximately 10,000 psia to approximately 15,000 psia, and for a duration of at least ten minutes and less than twenty minutes; and

a ribbon formed from a weave of nylon fibers secured to said body by heat fusion and having interstices and a thickness sufficient to wick an oil based liquid medium from said microporous skin. 

1. A DIRECT INKING PLATEN COMPRISING: A UNITARY NYLON BODY HAVING MIROPROUS INTERSTICES AND AN INTEGRAL FLEXIBLE-TOUGH MICROPOROUS OUTER SKIN PORTION, SAID BODY AND SKIN BEING FORMED FROM A COMPRESSION MOLDED PARTICULATE NYLON BLEND, SAID BLEND CONTAINING A MINORITY OF HIGH MESH NYLON PARTICLES WITH THE REMAINDER OF LOW MESH NYLON PARTICLES, SAID BLEND BEING COMPRESSED AT A TEMPERATURE FROM APPROXIMATELY 350* TO 420*F AND AT A PRESSURE FROM APPROXIMATELY 10,000 PSIA TO 15,000 PSIA FOR A DURATION OF AT LEAST TEN MINUTES AND LESS THAN 20 MINUTES, AND A RIBBON FORMED FROM A WEAVE OF NYLON FIBERS AND AFFIXED TO SAID BODY, THE RIBBON COVERING AND BEING CONTIGUOUS WITH AT LEAST A PORTION OF SAID FLEXIBLE-TOUGH OUTER SKIN.
 2. A direct inking platen comprising: a unitary nylon body and skin compression molded from a particulate nylon blend of disparate mesh nylon particles, said body having microporous interstices capable of transferring an oil based liquid medium throughout said body by capillary action, said body further having an integral flexible-tough outer skin portion, the micropores of which are randomly distributed; said body and skin being formed by compression molding of said blend of nylon particles at a temperature from approximately 350*F to approximately 420*F and at a pressure from approximately 10,000 psia to 15,000 psia for a duration of at least ten minutes and less than twenty minutes; and a ribbon formed from a weave of nylon fibers affixed to said body, said ribbon having substantially uniformly spaced interstices, the ribbon covering and being contiguous with at least a portion of said flexible-tough outer skin.
 3. A direct inking platen comprising: a unitary microporous nylon body having a porosity of from approximately 5% to approximately 15% and an integral flexible-tough microporous outer skin portion having a thickness on the order of approximately 1/5000 inches, said microporous interstices of said body being randomly distributed and capable of transferring an oil based liquid medium throughout said body by capillary action; said body and skin being formed from a compression molded blend of nylon particles, said blend being of a minority of nominal 80 mesh and the remainder of nominal 20 mesh particles, and being compressed at a temperature in the range from approximately 350*F to approximately 420*F and at a pressure in the range from approximately 10,000 psia to 15,000 psia for a duration of at least ten minutes and less than twenty minutes; and a ribbon affixed to said body formed from a nylon fiber weave of nominal warp count of 185 and nominal fill count of 115, and of a thickness from approximately 0.0030 inches to 0.0036 inches, said ribbon covering and being contiguous with at least a portion of said flexible-tough outer skin.
 4. A direct inking platen comprising: a unitary microporous nylon body capable of transferring an oil based liquid medium therethrough by capillary action and further having an integral flexible-tough microporous outer skin portion, said body and skin being formed from a compression molded blend of nylon particles, said blend being composed of a minority of nominal eighty mesh particles and the remainder of nominal twenty mesh particles, and being compressed at a temperature in the range from approximately 350* to approximately 420*F, at a pressure in the range from approximately 10,000 psia to approximately 15,000 psia, and for a duration of at least ten minutes and less than twenty minutes; and a ribbon formed from a weave of nylon fibers secured to said body by heat fusion and having interstices and a thickness sufficient to wick an oil based liquid medium from said microporous skin. 